Field of the Invention
In recent years, vehicles (hereinafter, collectively referred to as plug-in vehicles) such as electric cars or plug-in hybrid cars that can be charged by the use of an external power supply have been increasingly put to practical use. A dedicated charging cable having a control unit called a CCID (Charge Circuit Interrupt Device) is used to connect a plug-in vehicle to an external power supply.
The standard on an interface between the charging cable and the plug-in vehicle is defined by the “SAE (Electric Vehicle Conductive Charge Coupler) standard” of the U.S. or the “General Requirements for Electric Vehicle Conductive Charging System (the Japanese Electric Vehicle Standard)” of Japan. The charging sequence of a plug-in vehicle defined in the standard is substantially as follows.
First, a CCID of a charging cable transmits a control pilot signal (hereinafter, abbreviated as a pilot signal) to a charging-control ECU (Electronic Control Unit) mounted on a plug-in vehicle and determines that the charging cable is connected to the plug-in vehicle when the voltage of the pilot signal is changed from an initial value V1 (for example, 12 V) to V2 (for example, 9 V).
Then, the CCID of the charging cable informs the ECU of the plug-in vehicle of the rated current of a power supply facility by transmitting a pilot signal with a duty ratio corresponding to the rated current of the power supply facility (including an external power supply and a charging cable).
Subsequently, the ECU of the plug-in vehicle informs the CCID of the charging cable of completion of the preparation for charging by changing the voltage of the pilot signal from V2 to V3 (for example, 6 V).
Then, when detecting that the voltage of the pilot signal has changed from V2 to V3, the CCID of the charging cable determines that the preparation for charging of the plug-in vehicle side is completed, and turns on a relay used to supply the power of the external power supply to the plug-in vehicle (that is, starts the supply of power).
In this way, the pilot signal is a signal essential for controlling the charging of the plug-in vehicle and it is very important to detect abnormality of the pilot signal. For example, Japanese Unexamined Patent Application, First Publication No. 2009-71989 discloses a technique of detecting a disconnection of a control line used for transmission of a pilot signal in a state where a plug-in vehicle is connected to an external power supply via a charging cable.
Description of the Related Art
As described in Japanese Unexamined Patent Application, First Publication No. 2009-71989, the pilot signal is input to a processor such as a CPU via an input circuit (such as an input buffer) in an ECU of the plug-in vehicle. When the input circuit is out of order, the processor of the ECU is not started up or an appropriate charging control is not performed. Accordingly, a circuit for diagnosing the malfunction of the input circuit is necessary, but such a circuit is not disclosed in Japanese Unexamined Patent Application, First Publication No. 2009-71989.
The invention is made in consideration of the above-mentioned circumstances and an object thereof is to provide an electronic control unit that can diagnose a malfunction of an input circuit disposed in a stage preceding a processor performing a process necessary for a charging control based on a pilot signal.